Laser generator

ABSTRACT

Flow laminators are attached to gas introducing parts installed in a laser generator preventing impurities from attaching to surfaces of a translucent mirror and a condensing lens. The flow laminators prevent airflow from producing a turbulent flow and air on the surface of the mirror and the lens are cleaned up, therewith reducing attachment of impurities further.

This application is a U.S. national phase application of PCTinternational application PCT/JP2004/017322.

TECHNICAL FIELD

The invention relates to a laser generator exciting laser medium,amplifying a caused light with light amplifying mirrors, and outputtinga laser beam through one of the light amplifying mirrors as atranslucent mirror.

BACKGROUND ART

FIG. 3 is a constitutional drawing of a conventional laser generator. Inthe laser generator, power supply 32 excites laser medium 31.Translucent mirror (hereinafter, called mirror) 34 and laser lightamplifying mirror (hereinafter, mirror) 35 oscillate a caused light tobe generated as laser beam 36. Mirror holder 33A and 33B hold mirrors 34and 35, respectively. Mirror 34 is a translucent mirror allowing thelaser beam to be output to outside. Mirror 34 is generally called anoutput mirror.

Laser beam 36 which is amplified by mirrors 34 and 35 and output throughmirror 34 to outside passes through inside laser introducing duct(hereinafter, duct) 37 that protects the laser beam, shutter unit(hereinafter, shutter) 38, and light path duct 39 in this order. Thenthe light is reflected by reflecting mirror 40 and refracted bycondensing lens (hereinafter, lens) 41 to be utilized as a beam forlaser processing.

Shutter 38 is composed of reflect mirror 38A, actuator 38B drivingreflect mirror 38A, and absorber 38C absorbing the laser light reflectedby reflect mirror 38A. When laser beam 36 is not taken outside, actuator38B drives reflect mirror 38A into a path of the laser light reflectingthe light so as absorber 38C absorbs the laser beam reflected by reflectmirror 38A.

It is difficult to seal airtight components disposed outside mirror 34,i.e., duct 37, shutter 38 and light path duct 39 due to its structure.Consequently outside air containing oil, dust, iron powder and otherimpurities can flow into the components. If the air containing suchimpurities flows into the light path of the components and attaches tosurfaces of the mirrors and lens 41, the laser light may burn thesurfaces, which causes lowering power of the generator and damaging theoptical components seriously.

In order to prevent such incidence, Japanese Patent UnexaminedPublication Nos. S61-286085 and H3-60890 disclose a technology ofsending filtered air or nitrogen gas into a vicinity of the opticalcomponents of the generator. That is, the conventional laser generatorincludes gas supply source 42 supplying air, filters 43A and 43B, andgas introducing parts 44A and 44B which are air exhaust nozzles. Filters43A and 43B filter the air supplied by gas supply source 42, producingclean air. Gas introducing parts 44A and 44B send the clean air into avicinity of mirror 34 and lens 41 and clean up air in the vicinity ofthe optical components. Instead of air, gas supply source 42 can supplynitrogen gas using a commercially available nitrogen cylinder thatcontains fewer impurities.

The air or the nitrogen gas that purges impurities at the vicinity ofthe mirror 34 and lens 41 includes far less impurities than ordinary airdoes. However in the ordinary method where gas introducing parts 44A and44B forcefully blow out impurities, the blow out air is so called aturbulent flow having inconsistency in velocity and direction in thestream. Because of the reason, an eddy flow tends to occur inside duct37 and inside light path duct 39 near lens 41, inefficiently expellingout contaminated air already existing in duct 37 and light path duct 39,therefore impurities concentration on the surface of the mirrors andlens 41 is not thoroughly reduced.

The effect of air flow that purges impurities (air purge effect) on thesurface of mirror 34 can be examined by measuring oxygen concentrationnear the surface of mirror 34 by using nitrogen gas instead of air. Itmay be supposed that oxygen concentration on the surface of mirror 34 isreduced as the nitrogen flow increases, but actually the oxygenconcentration does not fall down below a certain level. Even whennitrogen flow is increased for reducing the oxygen concentration below100 ppm, the concentration is not in fact reduced lower than 0.2%(20,000 ppm) as long as the conventional air blowing method is employed.Thus, the method does not sufficiently protect components i.e. themirrors and the lens that are very sensitive to dust, oil and otherattached impurities, from performance deterioration caused by theimpurities.

In recent years, a demand for a high power laser generator is increasedand requirement for a higher energy density of the output light isaugmented. However, the optical components are not yet sufficientlyprotected from being contaminated so achievement of the high power ofthe laser is obstructed.

SUMMARY OF THE INVENTION

A laser generator of the present invention has a laser generating part,a laser-introducing duct, a light path duct, and a condensing lens. Thelaser generating part includes a mirror outputting a laser light. Thelaser-introducing duct guides the laser beam output by the lasergenerating part. The light path duct is installed next to thelaser-introducing duct and guides the laser beam. The condensing lens isplaced at an exit of the light path duct and condenses the laser beam.The laser generator has at least one of a pair of first gas introducingpart and a first flow laminator, and a pair of second gas introducingpart and a second flow laminator. The first gas introducing part isplaced near the mirror at the laser-introducing duct and introduces gasinto the laser-introducing duct. The first flow laminator is placed atthe first gas introducing part and regulating flow of the gas. Thesecond gas introducing part is placed near the condensing lens at thelight path duct and introduces the gas into the light path duct. Thesecond flow laminator is placed at the second gas introducing part andregulates flow of the gas. According to the constitution, gas suppliedto the laser-introducing duct and light path duct is laminated,effectively expelling out air containing impurities. Therewith,impurities on the surfaces of the output mirror and the condensing lensare reduced to a minimum level, providing the laser generator having astable laser output and an enhanced reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a constitutional drawing showing a structure of a lasergenerator in accordance with an exemplary embodiment of the presentinvention.

FIG. 2A is an enlarged sectional view of a main part of the lasergenerator shown in FIG. 1.

FIG. 2B is a conceptual sectional view of another flow laminator in thelaser generator shown in FIG. 1.

FIG. 2C is a conceptual sectional view of a still other flow laminatorin accordance with the exemplary embodiment of the present invention.

FIG. 3 is a constitutional drawing showing a structure of a conventionallaser generator.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 is a constitutional drawing explaining a structure of a lasergenerator according to an exemplary embodiment of the present invention.

In the laser generator, power supply 2 excites laser medium 1.Translucent mirror (hereinafter, mirror) 4 and laser light amplifyingmirror (hereinafter, mirror) 5 oscillate a caused light, generatinglaser beam 6. Mirror holder 3A and 3B hold mirror 4 and mirror 5,respectively. Because mirror 4 is a translucent mirror, the laser beamis allowed to be output to outside. FIG. 1 illustrates only one laserlight amplifying mirror, but two or more of the mirrors can beinstalled. Laser medium 1, power supply 2, and mirrors 4 and 5constitute a laser generating part.

Laser beam, amplified by mirrors 4 and 5 and output through mirror 4,passes through inside laser-introducing duct (hereinafter, duct) 7 thatprotects the laser beam. In other words, duct 7 directs the laser beamoutput by the laser generating part to outside. The laser beam thenpasses through inside shutter unit (hereinafter, shutter) 8 and lightpath duct 9 and the beam is reflected by reflecting-mirror 10 andcondensed by condensing lens (hereinafter, lens) 11 to be used as alaser-processing beam. Lens 11 is placed at an exit of light path duct 9that follows duct 7.

Shutter 8 is composed of reflect mirror 8A, actuator 8B driving reflectmirror 8A, and absorber 8C absorbing the laser beam reflected by reflectmirror 8A. When the laser beam needs not to be taken outside, actuator8B drives reflect mirror 8A into a laser light path, so that the laserbeam reflected by reflect-mirror 8A is absorbed by absorber 8C.

Gas supply source 12 is an air pump supplying air. Filters 13A and 13Bare composed of electrically charged resin fiber made of polyurethaneand polypropylene or of unwoven glass fiber, for example. Filters 13Aand 13B filtrate the air to remove impurities and produce clean air. Gasintroducing parts (hereinafter, introducing parts) 14A and 14B areexhaust nozzles of the clean air, and located near mirror 4 at duct 7and lens 11 at light path duct 9. In other words, gas supply source 12sends clean air through introducing parts 14A and 14B to vicinities ofmirror 4 at duct 7 and lens 11 at light path duct 9, cleaning up airnear the optical components. Instead of air, gas supply source 42 cansupply nitrogen gas or an inert gas such as argon and helium using acommercially available nitrogen gas cylinder containing fewerimpurities. In this case, filters 13A and 13B don't have to be disposed.Supply of air or gas is desirably controlled so that an inside pressureof duct 7 and light path duct 9 becomes higher than that of outside,preventing invasion of outside air.

Further in the exemplary embodiment of the invention, flow-laminators15A and 15B are respectively installed inside introducing part 14Aconnected to duct 7 and inside introducing part 14B close to lens 11.Flow laminators 15A and 15B regulate the clean air supplied by gassupply source 12 through filters 13A and 13B, producing a laminar flowof the air.

FIG. 2A is a sectional view showing details of duct 7 near mirror 4.Duct 7 is disposed with introducing part 14A, and introducing part 14Ais connected to air hose 17 through flow laminator 15A in a meshcondition. Air 21 led through air hose 17 to introducing part 14A issupplied to inside duct 7 by passing through flow laminator 15A.

When flow laminator 15A is not attached, air 21 supplied throughintroducing part 14A produces a turbulent flow of air having aninconsistent velocity and direction. This tendency becomes more distinctas the airflow is increased. Flow laminator 15A is attached to asubsequent place of introducing part 14A where a round shape mesh filteris placed. Because the mesh filter is placed in the air path, the airblowing through the mesh filter appears out as a consistent stream. Thephenomenon is theoretically identical water that is sprinkled by awatering pot.

One piece of the mesh filter can be placed; in this case the finer isthe mesh the higher becomes the laminating effect. However, becauseproducing a very fine mesh is difficult, a plurality of mesh filters canbe used in layers achieving an identical effect. A round shape meshfilter is preferable but a polygon shape filter also works. For materialof the mesh filter, a metal net can be used.

As described above, the laminar flow of air cleans the surface of mirror4 and prevents impurities from attaching to mirror 4. FIG. 2Aillustrates only duct 7. Because working principle is identical,explanation of a part of light path duct 9 near lens 11 is omitted. Adevice having a similar construction can be installed near mirror 10too.

FIG. 2B is a conceptual sectional view showing a more effective exampleof flow laminator 15A. In the example, four each of filters of 16A and16B having different mesh sizes each other are alternately placed inlayers. Number of the filters is not restrictive.

When filters having an identical mesh size are laminated, meshes areoften aligned, spoiling the effect of using a plurality of meshes. Onthe other hand, when four each filters 16A and 16B having different meshsizes are alternately laminated as shown in FIG. 2B, air inevitablyflows through the different sizes of meshes winding its way, achieving amore efficient laminar flow of the air.

FIG. 2C shows a structure of still other type of flow laminator 15A. Inthe constitution, filter 18 of thin wire such as stainless steel madelike a cotton ball is used in place of mesh filter 16A and 16B in FIG.2B. Air stream is as well laminated with the structure.

By installing above described flow laminators 15A and 15B, impuritiesconcentration in the air around the surfaces of mirror 4 and lens 11 iseasily reduced down to 100 ppm or less.

The clean air usually is sent into duct 7 and light path duct 9 forgetting rid of impurities during daytime when the laser generator isworking. Yet, outside air including impurities may get into duct 7 andlight path duct 9 during nighttime or holidays when the laser generatoris not working, attaching to the surfaces of mirror 4 and lens 11. Tokeep the optical components clean, the clean air is sent even when thegenerator is not working as well as during nighttime, securing a higherefficiency.

In above description, a pair of introducing part 14A and flow laminator15A and a pair of introducing part 14B and flow laminator 15B are bothinstalled, but only one of the pairs can be installed to either onewhere the affect of impurities are more serious.

INDUSTRIAL APPLICABILITY

A laser generator of this invention supplies gas to an introducing ductand to a light path duct after laminating the gas, thereby effectivelyexpels air including impurities to outside the generator. Therefore, anamount of impurities on surfaces of an output mirror and a condensinglens is reduced to a minimum level, providing an industrially usefullaser generator having a stable output and a high reliability.

1. A laser generator comprising: a laser generating part including amirror outputting a laser beam, a laser-introducing duct guiding thelaser beam output by the laser generating part, a light path ductinstalled next to the laser-introducing duct and guiding the laser beam,a condensing lens placed at an exit of the light path duct andcondensing the laser beam, and at least one of a pair of (a) a first gasintroducing part for introducing gas into the laser-introducing duct,and (b) a first flow laminator regulating a first flow of the gas sothat the first flow of the gas is a laminar flow on the mirror, or apair (a) second gas introducing part for introducing the gas into thelight path duct, and (b) a second flow laminator regulating a secondflow of the gas, so that the second flow of the gas is a laminar flow onthe condensing lens.
 2. The laser generator according to claim 1,wherein the at least one of the first or the second flow laminatorsincludes a mesh filter.
 3. The laser generator according to claim 2,wherein the mesh filter is one of a plurality of mesh filters, the atleast one of the first and the second flow laminators is composed of theplurality of the mesh filters placed in layers.
 4. The laser generatoraccording to claim 3, wherein the plurality of the mesh filtersincluding a first mesh filter and a second mesh filter having adifferent mesh size from the first mesh filter.
 5. The laser generatoraccording to claim 1, wherein the at least one of the first or thesecond flow laminator including a filter of thin wires made into a shapeof a cotton ball.
 6. The laser generator according to claim 1, whereinthe gas is supplied both when the laser generator is working and notworking.
 7. The laser generator according to claim 1, wherein the gas isone of an inert gas and nitrogen.
 8. The laser generator according toclaim 1 further comprising; a gas supply source supplying air, and afilter filtering the air supplied by the gas supply source, wherein atleast one of the first and the second gas introducing part uses the airfiltered by the filter as the gas.
 9. The laser gas generator accordingto claim 1, wherein at least one of pressure inside thelaser-introducing duct and the light path duct is higher than pressureoutside.
 10. The laser generator according to claim 1, wherein the firstgas introducing part is placed near the mirror at the laser-introducingduct and the first flow laminator is placed at the first gas introducingpart.
 11. The laser generator according to claim 1, wherein the secondgas introducing part is placed near the condensing lens at the lightpath duct and the second flow laminator is placed at the second gasintroducing part.